gd-libgd / src / gd_filename.c

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/* Convenience functions to read or write images from or to disk,
 * determining file type from the filename extension. */

#	include "config.h"

#include <stdio.h>
#include <string.h>

#include "gd.h"

typedef gdImagePtr (*ReadFn)(FILE *in);
typedef void (*WriteFn)(gdImagePtr im, FILE *out);
typedef gdImagePtr (*LoadFn)(char *filename);

#ifdef HAVE_LIBZ
static void writegd2(gdImagePtr im, FILE *out) {
    gdImageGd2(im, out, 0, GD2_FMT_COMPRESSED);
}/* writegd*/

static void writejpeg(gdImagePtr im, FILE *out) {
    gdImageJpeg(im, out, -1);
}/* writejpeg*/

static void writewbmp(gdImagePtr im, FILE *out) {
    int fg = gdImageColorClosest(im, 0, 0, 0);
    gdImageWBMP(im, fg, out);
}/* writejpeg*/

static void writebmp(gdImagePtr im, FILE *out) {
    gdImageBmp(im, out, GD_TRUE);
}/* writejpeg*/

static struct FileType {
    const char *ext;
    ReadFn reader;
    WriteFn writer;
    LoadFn loader;
} Types[] = {
    {".gif", gdImageCreateFromGif, gdImageGif, NULL},
    {".gd",  gdImageCreateFromGd,  gdImageGd, NULL},
    {".wbmp", gdImageCreateFromWBMP, writewbmp, NULL},
    {".bmp", gdImageCreateFromBmp, writebmp, NULL},

    {".xbm", gdImageCreateFromXbm, NULL, NULL},
    {".tga", gdImageCreateFromTga, NULL, NULL},

    {".png", gdImageCreateFromPng, gdImagePng, NULL},

    {".jpg", gdImageCreateFromJpeg, writejpeg, NULL},
    {".jpeg", gdImageCreateFromJpeg, writejpeg, NULL},

#ifdef HAVE_LIBTIFF    
    {".tiff", gdImageCreateFromTiff, gdImageTiff, NULL},
    {".tif" , gdImageCreateFromTiff, gdImageTiff, NULL},

#ifdef HAVE_LIBZ
    {".gd2", gdImageCreateFromGd2, writegd2, NULL},

    {".webp", gdImageCreateFromWebp, gdImageWebp, NULL},

    {".xpm", NULL, NULL, gdImageCreateFromXpm},


struct FileType *
ftype(const char *filename) {
    int n;
    char *ext;

    /* Find the file extension (i.e. the last period in the string. */
    ext = rindex(filename, '.');
    if (!ext) return NULL;
    for (n = 0; Types[n].ext; n++) {
        if (strcasecmp(ext, Types[n].ext) == 0) {
            return &Types[n];
        }/* if */
    }/* for */

    return NULL;
}/* ftype*/

  Function: gdSupportsFileType
    Tests if a given file type is supported by GD.

    Given the name of an image file (which does not have to exist),
    returns 1 (i.e. TRUE) if <gdImageCreateFromFile> can read a file
    of that type.  This is useful if you do not know which image types
    were enabled at compile time.

    If _writing_ is true, the result will be true only if
    <gdImageFile> can write a file of this type.

    Note that filename parsing is done exactly the same as is done by
    <gdImageCreateFromFile> and <gdImageFile> and is subject to the
    same limitations.

    Assuming LibGD is compiled with support for these image types, the
    following extensions are supported:

        - .gif
        - .gd, .gd2
        - .wbmp
        - .bmp
        - .xbm
        - .tga
        - .png
        - .jpg, .jpeg
        - .tiff, .tif
        - .webp
        - .xpm

    Names are parsed case-insenstively.


    filename    - Filename with tested extension.
    writing     - Flag: true tests if writing works


    GD_TRUE (1) if the file type is supported, GD_FALSE (0) if not.

gdSupportsFileType(const char *filename, int writing) {
    struct FileType *entry = ftype(filename);
    return !!entry && (!writing || !!entry->writer);
}/* gdSupportsFiletype*/

  Function: gdImageCreateFromFile

    Read an image file of any supported.

    Given the path to a file, <gdImageCreateFromFile> will open the
    file, read its contents with the appropriate _gdImageCreateFrom*_
    function and return it.  

    File type is determined by the filename extension, so having an
    incorrect extension will probably not work.  For example, renaming
    PNG image "foo.png" to "foo.gif" and then attempting to load it
    will fail even if GD supports both formats.  See
    <gdSupportsFiletype> for more details.

    NULL is returned on error.


    filename    - the input file name


    A pointer to the new image or NULL if an error occurred.


gdImageCreateFromFile(const char *filename) {
    struct FileType *entry = ftype(filename);
    FILE *fh;
    gdImagePtr result;
    if (!entry) return NULL;
    if (entry->loader) return entry->loader((char *)filename);
    if (!entry->reader) return NULL;

    fh = fopen(filename, "rb");
    if (!fh) return NULL;

    result = entry->reader(fh);

    return result;
}/* gdImageCreateFromFile*/

  Function: gdImageFile

    Writes an image to a file in the format indicated by the filename.

    File type is determined by the extension of the file name.  See
    <gdSupportsFiletype> for an overview of the parsing.

    For file types that require extra arguments, <gdImageFile>
    attempts to use sane defaults:

    <gdImageGd2>    - chunk size = 0, compression is enabled.
    <gdImageJpeg>   - quality = -1 (i.e. the reasonable default)
    <gdImageWBMP>   - foreground is the darkest available color

    Everything else is called with the two-argument function and so
    will use the default values.

    <gdImageFile> has some rudimentary error detection and will return
    GD_FALSE (0) if a detectable error occurred.  However, the image
    loaders do not normally return their error status so a result of
    GD_TRUE (1) does **not** mean the file was saved successfully.


    im          - The image to save.
    filename    - The path to the file to which the image is saved.


    GD_FALSE (0) if an error was detected, GD_TRUE (1) if not.


gdImageFile(gdImagePtr im, const char *filename) {
    struct FileType *entry = ftype(filename);
    FILE *fh;

    if (!entry || !entry->writer) return GD_FALSE;

    fh = fopen(filename, "wb");
    if (!fh) return GD_FALSE;

    entry->writer(im, fh);


    return GD_TRUE;
}/* gdImageFile*/